Gas-filled tube circuits



Oct. 4, 1932, B. G. BJGRNSON GAS FILLED TUBE CIRCUITS mun INVENTOI? Q G. RNSQIV 8V Filed June 20, 1930 GAS l /LLED T055 4 I Patented Oct. 4, 1932 AssIGnonr0 BELL rnLnrnonn LABORA- TORIES, INCORPORATED, OF NEW YORK, Y., A. CORPORATION NEWYORK eAs-rILLnn TUBE creams qApplication filed JimeQO,

The present invention relates to circuits employing electric space discharge tubes and particularly gas-filled tubes.

The invention has particular application to signaling systems in which certain switch ing operations ortransmission control functions are effected by the signals being transmitted through the system.: In systems of this type in the prior art it has been'common to utilize a portion of the speech 'or other signaling energy to control operation of an amplifier-detector circuit employing high vacuum tubes. The discharge current of these tubes is in turn used to actuate eleceromagnetic relays or to control directly a variable'loss element associated with the transmission circuit to vary the amount of loss between predetermined limits. In systems of this general character, among the important factors to be taken account of, maybe mentioned the operate time, sensitivity and uniformity of response of thecontrol circuits.

According to the present invention improved results are obtained by the use of gas filled space discharge tubes. It is found that more uniform response more positive operation, reduction of the operating time and greater sensitivity can be'secured for relatively the same amount of apparatus.

An object of the. invention is to improve the operation of circuits employing gas-filled tubes. A related object is to improve the construction and operation of signal-con trolled circuits in which gas-filled tubes are used. i

In accordance with thei'nvention, as will be more fullydescribed hereinafter, a gasfilled space discharge tube is'employed to effect operation of a circuit and an auxiliary control is used to supplement the control. exercized by the gas-filled tube. The auxiliary control may be slower in operation, less sensitive and may have a less uniform re- 1 V spouse, its main function being-first to maintain the circuit in the condition in which it was placed by the gas-filled tube, and then to cause positive release ofthe 'circuitQ In addition to maintaining the load circuit in itsoperated condition the auxiliary control also restores the gas-filled tube to its unoper- 1930. Scria1 No. 4=62,500.-:

ated condition. An incidental feature is a hang-over clrcuit associated with the auxiliary control. v

will be more fully under-' The invention stood from'the following description of "a terminal-echo suppressor circuit'as illustrated in the single figure of the accompanying drawing.

In the drawing hne L is shown terminating I in the usual hybrid coil generally indicated at 10, having a balancingimpedance 11If As-' sociat'ed with this hybrid'coilis an eastward transmitting branch 12 and a westward transmitting branch 13 v Transmission branch 12'1ncludes "amplifierl l' and a vacuum tube relay circuit 15' which mayals'o be arranged to amplify the signals, 'or not, as desired. This branch may also contain additional amplifiera not shown.,-

' The receiving branch 13' contains an am-' plifier 16. v Branched'across receiving circuit 7 His the input circuit 17 of an echo suppresg sor including inthe main control path amplifier stages 18 and 19 and a pair of gas-filled tubes associated in push-pull relation as inclicated at 20. This echo suppressor also includes an auxiliary control path including branch'circuit 21 and rectifier 22, the output of which includes relay 23.. 1 7

Associated with the transmitting branch 12' on the output side of vacuum tube relay 15' is a disabler circuit the input of which is shown at 24. Thiscircuit contains suitable amplifiers, one of which "is indicated at 25,

a rectifier 26 and relay 27'.

The operation of the circuit will now be described. In the absence of speech currents incoming on the line L,- the speech that is received over the westward channel 13 is impressed through the hybrid coil 10' upon line L and at same time the branch 12' is rendered incapable of transmission by disabling vacuum tube relay 15 in a manner to be described.

j- A small portion of the received'speech in branch 13 passes into circuit 17, is amplified at 18 and 19, and is impressed on the grids' of the gas-filled tubes 20. The amplification introduced at 18 and 19 controls the sensitivity of the ci'rcuit' and this is preferably made condition. A rush of current then flows from ground at 30, through resistance 31, battery 32, back contactof' armature of relay 27, upper winding of relay 23, throughspace paths .of gas-filled tubes to ground.

This sudden rise of current through resistance 31 places a large negative bias on the grids of the tubes of vacuum tube relay 15 placing this circuit in the high loss condi 'tion and preventing transmission in the eastward branch 12. a a

V This current also causes relay 23 to energize and attract its armature. Relay 33 then is energized by currentfrom battery 34, through the resistances shown and through the front contact of relay 23. Relay 33 in attracting its armature closes a shunt path to ground sistance has a sufliciently low value wit through resistance 35 in parallel with the space paths of the gas-filled tubes 20. Re

respect to the constants oftubes 20, battery 32 and resistance 31 that the anode Voltage of tubes 20 is reduced to a point where space current no longer flows through these tubes.

' that relays 23 and 33 are both maintained That is, tubes 20 are restored to their normal high impedance non-conducting condition. However, the current through resistance 31 is maintained by the existence of the circuit through resistance 35 under control ofrelay 33. Relay 23 is continued energized by rectified speech in the output of tube'22, the circhit of which includes a second winding of relay 23. Vacuum tube relay 15 is maintainedin its high loss condition so long as relay 33 remains energized. It will be noted energized independently of gas-filled tubes 20 so long as speech is present in branch 13.

When the speech waves cease in branch 13 relay 23 is deenergized causing its armature to open the energizing circuit of relay 33. The latter relay does not immediately release, however, since charging current now begins to flow into condenser 38 from battery.

34 through the winding of relay 33. The purpose of this condenser is toprovide a hold-over effect for relay 33. The length of the hold-over can be adjusted by proportion ing the capacityof condenser 38 in relation to the resistance and inductance of the circuit as a whole. When relay 38 becomes suffi ciently charged and the current in relay 33 is sulficientlylow, this relay releases its armature and breaks thecircuit through resist ances 31 and 35 and battery 32. This re+- moves the disabling bias fromthe grids of the vacuum tubes 15 and restores the east- 12 to its normal transmitting.

ward 1 circuit condition. 7

.. In the event that the talkingparty on line,

L has begun to speak before speech arrives over line 13 at-the terminal shown in the drawing, the echo suppressor is ineffective in disabling branch 12. It will be understood, of course, that at the remote terminal the echo suppressor 17, 18, 19, 20 will be associated with branch 12' (which at that terminal is the receiving branch) and the disabler 24, 25, 26 will be associated with branch 13. It is seen therefore thatth'e speaker whose-voice reaches the far terminal before relay 27 there- I at becomes energized by the opposite speakh the output side of vacuum tuberelay 15, positive control of the latter is given to the echo suppressor and false operation of the disabler is minimized. That is, relay 27 is only operated on condition that-circuit 15 is able to transmit. Amplifier 18 is shown provided with a condenser 40 across its input and amplifier 19 is provided with a potentiometer 41 in its input circuit, These elements are for the purpose of adjusting the amplitude-frequency responseof the echo suppressor in proper relation to that'of the disabler circuit 24, 25, 26. It is a characteristic of the gas-filled tubes 20 that they either remainunoperated, or are fully operated by the impressed speech waves. This fact makes for positive operation of the circuit. It will be noted that relay 23 has its actuating winding in the circuit of the gasfille'd tubes 20. If this were not done and if relay 23 were energized solely under control of waves in the path 2122,- it might happen that relay 23 would failto respond to speech waves of low amplitude, but of suflicient amplitude to cause breakdown of the tubes 20.

The circuit as arranged insures that relay 23.

is operated whenever tubes 20 operate. Re-

lay 23 can be maintained operated by a smaller current than is required to energize it in- 1t1al1y. This arrangement msures both ,posi-- t1ve operationand maintenance in the operated condition. throughout the duration of speech waves in line 13.

The gas-filledtubes 20 may be of any suit practice they will, of course, be supplied with filament heating batteries or the equivalent. For a more complete disclosure of the construction of gas-filled tubes 20, reference may be made to A. L. San1uel,-application Serial No. 465,083, filed July 1, 1930.

What is claimed is:

1. The combination with a load circuit to be operated of a gas-filled electric discharge device and an auxiliary control, an input circuit common to both, means for operating said load circuit under control of either said device or said auxiliary control, said gas-filled device acting in response to an impulse in said input circuit to initially operate said load circuit, said auxiliary control acting to maintain the load circuit in operated condition imder control of said input circuit.

2. The combination with a load circuit toload circuit under control of either said tube or said auxiliary control, said gas-filled tube having a conducting and a non-conducting condition and acting in response to a wave in said input circuit to initially operate said load circuit, said auxiliary control acting in response to said wave to restore said tube to its non-conducting condition and to maintain said load circuit in operated condition independently of said tube.

3. The combination according to claim 2 in which said auxiliary control has a hangover control maintaining said load circuit in operated condition for a predetermined time interval after cessation of the wave in said input circuit.

l. In a signal operated system, a path for the transmission of signals, a disabling circuit for determining the operative or non-operative condition of said path in response'to impressed signals, said circuit comprising a gas-filled tube responsive to said signals for initially controlling said path, and an auxiliary control also responsive to said signals for controlling restoration of the path to its alternative condition.

5. In a voice-operatedsystem, a transmission element of variable loss associated with a speech transmission path forrcontrolling transmission therecver, means comprising a gas-filled space discharge tube having an operated and a nonoperated condition, said tube being operated in response to voice energy for controlling the loss of said element, and an auxiliary control responsive to voice energy for restoring said tub-e to its unoperated condition and maintaining the control of said loss element.

6. The combination with a load circuit to be operated, of a gas-filled tube and an auxiliarycontrol, a common input circuit for both, said auxiliary circuit comprising an electromagnetic relay having an armature, and a substitute circuit for the gas-filled tube circuit controlled by said armature, and means for operating said load circuit under control of either said gas-filledtube or said relay armature.

7 The combination according to claim 6 in which said gas-filled tube has a normal high impedance condition and a low impedance condition and said substitute circuit when closed under control of said relay armature shunts the space path of the gas-filled tube and restores said tube to its high impedance condition.

8. The combination with a signal transmission path of a circuit for disabling the same, a gas-filled tube responsive to signal Waves for controlling operation of said disabling circuit, an auxiliary circuit also controlling said disabling circuit, said auxiliary circuit including a relay having an energizing winding in the path of the space current of said gas-filled tube, and a holding winding onbsaid relay independent of said gas-filled tu e.

9. The combination with a signal transmission circuit of a circuit for disabling the same, a gas-filled tube responsive to signal waves for controlling said disabling circuit, an auxiliary control also responsive to signaling waves for maintaining control of said disabling circuit independently of said gasfilled tube, and a hold-over relay included in said auxiliary circuit for maintaining control of the disabling circuit after the cessation of signal waves.

10. The combination with a speech transmission path and a transmission control element therein, of a hot cathode gas-filled discharge tube for' altering the transmission characteristic of said control element, said tube having a high impedance zero current condition and a low-impedance, high current condition, means responsive to received speech for changing said tube from its high impedance condition to its high current condition to, in turn, alter the transmission characteristic of said control element, and a disabler circuit controlled by speech waves in said speech transmission path for interruptingthe connection between said gas-filled tube and said transmission control element.

11. The combination defined in claim 10in which said disabler circuit has its input circuit connected on the output side of said transmission control element.

In Witness whereofll hereunto subscribe my name, this 19th day of June, 1930.

BJORN e. BJonNsoN. 

